Downlights Issues - Fire rating/Insulation/LED/Efficiency

I have new single storey kitchen extension with a V shaped pitched ceiling and roof, which has a 150mm void, and want to install some downlights.

Please could someone confirm whether I need a fire-rated downlight (i.e. I am not sure if a ceiling/roof in my scenario, which does not have a living space above it, is covered by the regulations). I could not find the relevant section in the part B regulations booklet.

Irrespective of the above, is it OK to lay insulation around the downlight, or must this be cut back, or should an insulation guard be fitted. I will probably go for the aluminium reflector type to avoid heat being sent to the rear.

I know LED downlights can solve the heat issue, but I have read they do not give sufficient light? Would be interested to hear from anyone who has these installed.

Lastly, are the energy efficiency requirements that 1 in 4 lights need to be EE or 1 light per 25mm2 area, or do both these criteria have to be met? My extension is 50mm2 and so do I just need 2 EE lights, even though I will probably have 20 lights in total.

I have new single storey kitchen extension with a V shaped pitched ceiling and roof, which has a 150mm void, and want to install some downlights.

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There is no way any halogen downlights can be installed there, and still be compliant with building regulations.
The void will need to be insulated, and all halogen downlighters require clear space above them - typically at least 150mm, sometimes more.

Cutting holes in the insulation is no good, since the insulation is required.
Covering the downlighters with insulation is no good either, since they will overheat and either cease working, cause a fire, or both.

Discharge lighting will solve heat problem although with 50mm lamps they can take with GU10 fittings tungsten, discharge or LED and one would need to do something to stop tungsten being fitted. With 150mm down lights discharge fittings can be used so no mistakes can be made latter. The other option is pods where the lights stick out of the ceiling.

The 50mm lamps have a very narrow angle and getting general lighting with such a small angle means the ceiling will look like a planetarium and although they do help the look of the room they seem to give out less light than a TocH candle so really it needs discharge lighting which could be supplemented with 50mm units rather then rely on just 50mm units.

Using low voltage rather than extra low voltage fitting does allow the use of discharge units, that is florescent or cold cathode which are better than LED units but the lamps are often longer than the tungsten versions and you have to be very careful with selection so they can take extra depth.

The 150mm units can use either lamps designed to replace the tungsten bulb or the 2D types both have many sizes but one can fit 28W and compared with the 11W of the 50mm units they seem to give 3 or 4 times the light output mainly because of spread pattern.

With a V shaped ceiling I would think florescent tubes in the apex with white panel below to reflect the light as seen in many airports would give light without being seen.

If the florescent is going to be hard to access using HF type will give a lot longer life and one should not have to touch them for 5 years. Of course no guarantee but we used them over machines both as no stroboscopic effect and low maintenance.